Siemens SIMATIC S7 System Manual page 527

Network 3: State "Connect"...
Start the connection process.
Network 4: Create an active connection to the passive device.
The program only calls the TCP_CONNECT instruction one time in this state. Set the Req
input to TRUE to start the connection process. Since this is the active side of the connection,
the instruction sets the Active input to TRUE.
Network 5: If Done is TRUE, the CPU established the connection to go to the "Idle" state.
If Busy is TRUE, go to the "Connect Wait" state to wait for the connection to be established.
If Error is TRUE, there is probably an error with the input parameters, so check to see what
state to go to next.
In all cases, exit the state machine for this scan. The program continues to the next state on
the next scan.
Network 6: State "Connect Wait"...
Wait in this state until there is a connection created to the passive device.
S7-200 SMART
System Manual, V2.3, 07/2017, A5E03822230-AF
9.4 Open user communication library
Libraries
527